task: override env vars on exec

syscall.Exec does not override env vars, it just seems to send all
env vars, even duplicates. This fixes the issue.

task/task.go

@@ -5,6 +5,7 @@ import (
  "os"
  "os/exec"
  "path/filepath"
+ "strings"
  "syscall"
 
  "github.com/mattn/go-shellwords"
@@ -93,7 +94,33 @@ func (t *Task) RunExec(args []string) error {
  return err
  }
 
- env := append(os.Environ(), t.Env...)
+ env := merge(os.Environ(), t.Env)
  args = append(fields, args...)
  return syscall.Exec(path, args, env)
 }
+
+// Merge merges the given two lists of env vars.
+func merge(a, b []string) []string {
+ var items = make(map[string]string)
+ var ret []string
+
+ for _, item := range a {
+ if i := strings.Index(item, "="); i != -1 {
+ key := item[:i]
+ items[key] = item[i+1:]
+ }
+ }
+
+ for _, item := range b {
+ if i := strings.Index(item, "="); i != -1 {
+ key := item[:i]
+ items[key] = item[i+1:]
+ }
+ }
+
+ for k, v := range items {
+ ret = append(ret, k+"="+v)
+ }
+
+ return ret
+}